Turbofan gas turbine engines have a fan mounted at the front of the engine. The fan increases the volume of air that enters the engine, helping to provide additional thrust.
The fan is situated upstream of the compressor and is mounted on a fan shaft that is driven to rotate by one of the engine turbines. The fan shaft typically encloses a thin-walled “fan retention” shaft mounted coaxially with the fan shaft. The fan retention shaft is designed to retain the fan in the event that the fan shaft should fail, following exposure to an axial overload, for example. The fan retention shaft can absorb impact energy by deforming elastically. In order for the fan retention shaft to fulfil its function, it is necessary to choose a material that has sufficient ductility to absorb the impact energy without breaking. Currently, the materials that satisfy this requirement tend to be heavy and place an extra weight burden on the engine, leading to reduced engine efficiency.
There is thus a continuing need to develop fan retention shafts for use in gas turbine engines.